1. Field of the Invention
The present invention relates to a process for making a fasciated spun yarn.
A fasciated yarn spinning process is a process having high production efficiency in which the fasciated spun yarn, having fibers wrapping around and fasciated with core fibers composed of substantially untwisted staple fibers, is made by a single step of false twisting a bundle of fibers composed of drafted staple fibers under overfeed conditions.
2. Description of the Prior Art
In the fasciated yarn spinning processes of the prior art, if the spinning step is conducted at a low overfeed ratio, untwisted portions having no wrapping fibers are formed making it difficult to produce a practical yarn. It is, therefore, necessary in the prior art processes to have the overfeed ratio exceed at least 5%. When the overfeed ratio is raised, however, problems arise in that the yarn has an uneven appearance and hard feel, characteristics which are far different from those of the usual ring-spun yarn.
Representative of the prior art is a well known process which uses an aspirator, as is disclosed in U.S. Pat. No. 3,079,746. This process is not effective in the stable delivery of fibers because the air flow in the passage becomes a turbulent flow and has high fluctuations.
As another means, there is a pneumatic suction tube which uses a suction air flow so that it allows a yarn to linearly pass therethrough, as has been disclosed in U.S. Pat. No. 4,003,194. This process is excellent in that the air flow is little disturbed to ensure stability in delivery but insufficient floating fibers are generated by merely using a cylindrical tube, tus making it difficult to spin a strong yarn.
According to another process disclosed in U.S. Pat. No. 4,112,658, two false twisting nozzles having opposite false twisting directions are used in series to form surface wrapping fibers. However, this process is not completely satisfactory partly because compressed air consumption is raised by the use of two nozzles and partly because the surface wrapping fibers are tightly wound producing a yarn with a hard hand.
A process relating to the technique which is the most similar to the present invention among the prior art examples thus far described, as has been disclosed in U.S. Pat. No. 4,003,194, will be described in detail in the following by way of example. This process is conducted by drafting fasciated staple fibers and transferring them while being fed to those aprons which can propagate the false twist given downstream thereof to its nip point upstream thereof in their open state, by false twisting fibers present mainly in the middle portion of the aprons thereby generating peripheral fibers, which are free from being restricted at both ends from the false twisting action or in a similar state, around these false-twisted fasciated fibers, and by subsequently wrapping the aforementioned peripheral fibers upon the false-twisted fasciated fibers leaving the false twisting means in a direction opposite to the false twisting direction.
The spun yarn made by the process described above is structured such that the main fibers occupying a major portion of the spun yarn are in a substantially untwisted state and are wrapped by the free fibers (i.e., the peripheral fibers). As a result, the strength and the hand, the extent of binding irregularities, etc. of the spun yarn are highly dependent upon the amount and the state of wrapping of the free fibers.
In this fasciated yarn spinning process, if the spinning step is conducted at a low overfeed ratio, untwisted portions having no wrapping fibers are formed, making it difficult to make a practical yarn. It is, therefore, necessary to have the overfeed ratio exceed at least 5%. When the overfeed ratio is raised, however, problems arise in that the yarn has an uneven appearance and a hard feel, characteristics which are far different from those of the usual ring-spun yarn.